Ophthalmological device

ABSTRACT

An ophthalmological device ( 1 ) comprises an optical transmission system ( 5 ) for transmitting femtosecond laser pulses to a projection objective ( 3 ) for projecting the femto-second laser pulses onto or into eye ( 2 ) tissue. The ophthalmological device ( 1 ) further comprises an objective changing device ( 4 ) for changing and connecting the projection objective ( 3 ) to the optical transmission system ( 5 ). The objective changing device ( 4 ) comprises more than one different projection objectives ( 3 ) connected mechanically with each other, and the objective changing device ( 4 ) is configured to convey one of to the projection objectives ( 3 ) to the optical transmission system ( 5 ) for connecting the respective projection objective ( 3 ) to the optical transmission system ( 5 ). The objective changing device ( 4 ) makes it possible to adapt the laser-based ophthalmological device ( 1 ) for new applications without the need for extensive reconfigurations and/or costly vario-lense objectives.

CROSS REFERENCE TO RELATED APPLICATIONS

The present application is a continuation of prior application Ser. No.12/139,126 filed Jun. 13, 2008, entitled OPHTHALMOLOGICAL DEVICE, whichis a continuation in part of prior application Ser. No. 11/822,401 filedJul. 5, 2007, entitled OPHTHALMOLOGICAL DEVICE which claims benefit ofand priority to European Patent Application No. 06405317.6 filed Jul.21, 2006, the entire content of each of which is hereby incorporated byreference herein.

BACKGROUND

1. Technical Field

The present invention relates to an ophthalmological device forprojecting femtosecond laser pulses. The present invention relates, inparticular, to an ophthalmological device is with an optical lightprojection module for projecting deflected femtosecond laser pulses ontoa defined treatment surface into an image area extending from theoptical axis of the light projection module.

2. Prior Art

Simple spherical lenses focus at the focal point only monochromaticlight beams which run near the optical axis (paraxial beams). Beamsrunning that are further removed from the optical axis are focused atanother focal point. This most common image error is termed apertureerror, or else spherical aberration. If the aim is to focus with a highnumerical aperture in order to attain small spot sizes, it is possibleto compensate these errors by aspheric lens shape, for example. Thiscompensation provides no assistance for imaging locations lying off theoptical axis. In addition, further aberrations such as coma, fieldcurvature, astigmatism or distortions result during optical imaging.Furthermore, axial and lateral chromatic aberrations occur whenpolychromatic light is being used.

It is normal to use a combination of a number of spherical lenses withdifferent refractive properties to compensate these errors. Diffractiveoptical elements are also used for this purpose in a few cases. Ingeneral, the outlay on correction, and thus the number of opticalelements (for the most part lenses and mirrors) and materials which areused rises with the numerical aperture and the field size (size of thesharply focused image area). However, the diameter and the weight of theoptical systems also rise substantially with the numerical aperture andthe field size. When the focal plane is additionally to be adjusted, theoutlay on equipment rises further. This relationship is of greatimportance particularly in the design of femtolaser systems. Forexample, femtolaser systems, which have pulse widths of typically 10 fsto 1000 fs (1 fs=10−15 s), require numerical apertures of greater than0.2 in an ophthalmological application, since otherwise the materialremoval at depth (for example in the cornea) is not accurately defined,and optical breakthrough already comes about partially on structureslying above the focal plane (for example in the epithel). A furtherundesired phenomenon outside the focal plane are streaky structures(so-called “streaks”) in the tissue along the propagation direction ofthe laser beam. There are breakthroughs above and below the focal planeeven in the case of systems with numerical apertures around 0.3. Highlycorrected systems with a working area of 10 mm with a numerical apertureof 0.3 require as many as ten and more lenses with a diameter of about100 mm. Raising the numerical aperture is possible in practice only inconjunction with a reduced image field (image area). In addition, in thecase of phases of femtosecond laser pulses which are affected byaberrations, there is the problem that not all light beams come intofocus at the same instant, because of different transient times.Particularly in the case of very short pulses, the maximum intensity atthe focus is therefore reduced.

By way of example, Patent Application EP 1486185 describes such anophthalmological device with an application head which can be usedmanually, and in this case the advantages of the small overall size andthe low weight are bought at the expense of the disadvantage of arestricted image field.

Patent Application DE 10358927 describes a laser device for materialmachining by means of laser radiation, in particular for refractivesurgery on the human eye by means of deflected femtosecond laser pulses.The device according to DE 10358927 comprises a pulse selection devicewhich modifies selected laser pulses such that the modified pulseseither no longer pass into the material to be machined at all, or can atleast no longer produce an optical breakthrough there. The modificationof the laser pulses comprises influencing parameters such as phase,amplitude, polarization, beam direction and field distribution over beamcross section (beam profile). By means of wavefront modification, inparticular, the selected laser pulses are defocused such that the energydensity no longer suffices for optical breakthroughs. The pulseselection, and thus the modification, perform, in particular, in afashion synchronized with the deflection rate.

SUMMARY

It is an object of the present invention to propose an ophthalmologicaldevice for projecting deflected femtosecond laser pulses which does nothave the disadvantages of the prior art. In particular, it is an objectof the present invention to propose an ophthalmological device forprojecting deflected femtosecond laser pulses which enable an enlargedimage field in the case of a given projection optics, known from theprior art, in conjunction with retention of the central image qualityeven in the edge regions of the treatment surface (for example focalplane). It is, in particular, a further object of the present inventionto propose an ophthalmological device which is of such a small designand such a low weight that it is suitable for manual application andpositioning. Furthermore, the aim is to enable the use of differentapplanation elements and/or interchangeable objectives through thepossibility of being able to adapt the optics.

In accordance with the present invention, these objects are achieved, inparticular, by means of the elements of the independent claims. Furtheradvantageous embodiments proceed, furthermore, from the dependent claimsand the description.

The ophthalmological device comprises an optical light projection modulefor projecting deflected femtosecond laser pulses into an image area,extending from the optical axis of the light projection module, on adefined treatment surface.

The above named objects are achieved with the aid of the presentinvention by virtue, in particular, of the fact that theophthalmological device is also provided with a controllable opticalcorrection element and a control module connected thereto, thecontrollable optical correction element being set up to modulate thewavefront of the femtosecond laser pulses in a variable fashion, and thecontrol module being set up to control the correction element as afunction of a deflection of the femtosecond laser pulses in such a waythat the femtosecond laser pulses are focused in the image area. Thecontrollable optical correction element and the control module arepreferably set up to modulate the wavefront of the femtosecond laserpulses sequentially in each case for an image point lying inside theimage area and onto which the deflected laser beam is projected. Thesequential correction of the wavefront is performed image point by imagepoint, in accordance with the scanning pattern of the deflected laserpulses, and is significantly less complex and complicated than acorrection of an overall image with a multiplicity of image points whichare to be projected simultaneously into the image area. The controlledmodulation of the wavefront enables the focused projection of thefemtosecond laser pulses onto the treatment surface in the entireextended image area arranged about the optical axis of the lightprojection module. The modulation of the wavefront enables evenfemtosecond laser pulses from pulsed laser beams which run that run at adistance from the optical axis of the light projection module to beimaged onto the machine surface in a fashion focused in the image area.It is possible by means of the adaptive and dynamic modulation of thewavefront of the deflected femtosecond laser pulses for the femtosecondlaser pulses to be focused onto the treatment surface in an enlargedimage area in conjunction with unchanged projection optics of the lightprojection module and so the image field can be enlarged in conjunctionwith an unchanging compact design of a light projection module suitablefor manual application. The image quality of the optics of the lightprojection module can be generally improved by means of the correctivemodulation of the laser pulse wavefronts. The controlled modulation ofthe wavefronts enables the more cost effective provision of a highlycompensated optical system with a relatively small number of opticalelements, a design that is smaller overall and a lesser resulting weightthan optical systems of the prior art. In particular, the controlledcorrection module enables an ophthalmological device to be designed witha compact, manually positionable light projection module which is notfelt to the patient to be threateningly large and has an image field ofat least 10 mm and a numerical aperture of at least 0.3. Smaller imagefields or image areas, for example with the diameter of 1 2 mm, 3 5 mmor 6 9 mm, can, in particular, be achieved with the design which isfurther reduced and yet more compact. Moreover, inaccuracies infabrication and assembly, as well as aberrations can be compensated bymeans of lightweight optical superstructures in conjunction withregulated operation.

In one embodiment, the ophthalmological device comprises a detectormodule with a wavefront detector and/or a light beam profile detectorfor determining a wavefront profile or a light beam profile of thefemtosecond laser pulses, and the control module is set up to controlthe correction element as a function of the specific wavefront profileor light beam profile. The wavefront of the femtosecond laser pulses canbe dynamically modulated, and therefore dynamically detected forfocusing the femtosecond laser pulses in the image area by means ofcontrolling the correction element on the basis of the detectedwavefront profile or light beam profile.

In a further embodiment, the ophthalmological device comprises opticalelements for detecting the femtosecond laser pulses projected into theimage area, and the control module is set up to control the correctionelement as a function of detected femtosecond laser pulses projectedinto the image area. The detection of the femtosecond laser pulsesprojected into the image area permits the projection quality actuallyproduced in the image area, for example with the assistance of theabovementioned detector module, to be fed back and determined in afashion as free from error as possible.

In one embodiment, the ophthalmological device comprises opticalelements for simulating a reference beam path corresponding to a beampath used for projecting the femtosecond laser pulses onto the treatmentsurface, and for detecting femtosecond laser pulses projected in thereference beam path. In addition, the control module is set up tocontrol the correction element as a function of detected femtosecondlaser pulses projected in the simulated beam path. The detection of thefemtosecond laser pulses projected in the reference beam path permitsthe projection quality to be fed back and determined, for example withthe aid of the abovementioned detector module, without intervening (thatis to say inserting optical elements) in the beam path used for themachining.

In one embodiment, the ophthalmological device comprises a laser sourcefor generating a reference laser beam, and the control module is set upto control the correction element as a function of the reference laserbeam deflected and projected in accordance with the femtosecond laserpulses. Depending on the variant, the reference beam path is led via thebeam path used for the machining or the reference beam path.

In one embodiment, the control module comprises control data with anassignment of control values to deflection values, and the controlmodule is set up to control the correction element on the basis of thecontrol values which are assigned to current deflection values. Thecontrol based on defined control data enables, inter alia, a controlwithout feedback based on knowledge of the geometry of theophthalmological device.

In one embodiment, the ophthalmological device comprises opticalelements for detecting the femtosecond laser pulses projected into theimage area, and a calibration module for generating and storing thecontrol data as a function of detected femtosecond laser pulsesprojected into the image area. In one variant, the calibration module isset up to generate the control data as a function of the wavefrontprofile or light beam profile determined by the detector module. Bymeans of the calibration, the control data can, on the one hand, bereadjusted and, on the other hand, be adapted upon application tocircumstances and requirements specific to machining.

In a number of embodiments, the optical correction element is set upsuch that during the modulation of the wavefront of the femtosecondlaser pulses it varies phase distribution, amplitude distribution,polarization distribution and/or propagation directions in the beamcross section of the femtosecond laser pulses.

In a further embodiment, the ophthalmological device comprises a holdingelement for changeably holding at least one objective element of theoptical light projection module. The holding element enables, forexample, the interchanging of the entire light projection module or ofan objective or objective element (for example one or more lenses) ofthe light projection module. In particular, the holding element enablesthe holding or the interchanging of various light projection modules,objectives or objective elements, which are set up for the (focused)projection of deflected femtosecond laser pulses into image areas ofdifferent size and/or onto various treatment surfaces, which machinesurfaces are, for example, defined (that is to say shaped) by variouscontact elements to be flat (applanation surface) or curved(spherically, convexly). The controllable optical correction element andthe control module are, moreover, set up to modulate the wave-front ofthe femtosecond laser pulses such that projection errors resulting fromthe mechanical interchange of the light projection modules, objectivesor objective elements are compensated or corrected.

In a number of embodiments, the optical correction element comprises adeformable mirror, a spatial transient time delay element, moveablelenses, moveable prisms, a diffractive optical element, and ananamorphotic optical module, a photonic crystal, a lens array, a spatialpolarization plate, a diaphragm and/or a spatial light modulator.

In a further aspect of the present invention, the ophthalmologicaldevice for treating eye tissue using femtosecond laser pulses comprisesan optical transmission system for transmitting the femtosecond laserpulses to a projection objective for projecting the femtosecond laserpulses onto or into the eye tissue. The above-mentioned holding elementis implemented as an objective changing device, i.e. theophthalmological device further comprises an objective changing deviceconfigured for changing and connecting the projection objective to theoptical transmission system. The objective changing device makes itpossible to adapt the laser-based ophthalmological device for newapplications without the need for extensive reconfigurations and/orcostly vario-lense objectives. The objective changing device makes itpossible for a user to interchange flexibly and efficiently theprojection objective, so that the projection objective can beinterchanged without significant time delay in between differentapplications and treatment steps. Particularly, the objective changingdevice makes it possible to adapt the system to new applications whichwere not known or in use at the time the system was manufactured.Compared to the use of vario-lense objectives, interchanging projectionobjectives is further advantageous in that there is no need forcontrolled settings of objective parameters, and thus no requirement ofrespective components and modules for parameter feedback and control.

In a preferred embodiment, the objective changing device comprises morethan one different projection objectives connected mechanically witheach other, and the objective changing device is configured to supplyone of the projection objectives to the optical transmission system forconnecting the respective projection objective to the opticaltransmission system. For example, the projection objectives differ intheir focal length, field size, field curvature, numerical aperture,focus diameter, focus shape, focus extension in projection direction,and/or beam divergence. In different embodiments, the objective changingdevice is configured to interchange the projection objectives throughrotary or translatory motion, in each case, one of the projectionobjectives is supplied to the optical transmission system through rotaryor translatory motion for connecting the respective projection objectiveto the optical transmission system. An objective changing device havingmultiple projection objectives makes possible a particularly efficientinterchange by way of simple manipulations, without the necessity ofattaching new projection objectives to the ophthalmological deviceduring the treatment.

In further embodiments, the projection objectives comprise in each casean application element for applying the projection objective onto aneye, and/or the ophthalmological device comprises a common applicationelement for applying the projection objective onto an eye, whereby theobjective changing device is configured to combine the projectionobjective with the application element when connecting the respectiveprojection objective to the optical transmission system. The variantwith multiple application elements, in each case connected to aprojection objective, has the advantage that different applicationelements can be interchanged by way of simple manipulations,independently from the projection objective, e.g. application elementshaving different contact forms or working distances. In a combinationembodiment, it is possible to interchange different application elementsand/or projection objectives as well as to provide a common applicationelement, e.g. used for fixing onto the eye.

In a further embodiment, the objective changing device comprises atleast one connecting module for removably receiving and connecting theprojection objective to the optical transmission system. A combinationof the connecting module with an objective changing device makes itpossible to load, before an operation, the objective changing devicewith suitable, application and/or patient-specific projection objectivesand/or application elements, and to interchange a selected elementduring the operation without further manipulations by way of a rotary ortranslatory motion. An objective changing device with only oneconnecting module makes possible a particularly simple device embodimentwhich permits the selection and interchanging of different projectionobjectives during the operation.

Preferably, the optical transmission system is configured to convey thefemtosecond laser pulses to the projection objective by way of beamswhich are essentially parallel. Beams which enter the projectionobjective in parallel have the advantage that imprecision of themechanical interchanging of different projection objectives (mountingtolerances) do not have an impact on the focal depth achieved with theprojection objective.

In an embodiment, the ophthalmological device comprises a measurementsystem for determining for the projection objective connected to theoptical transmission system its position relative to the device. Themeasuring system makes possible the detection, indication and/orcorrection of imprecise positioned projection objectives.

In a further embodiment, the ophthalmological device comprises adetector for determining an objective type identifier provided by theprojection objective connected to the optical transmission system.Preferably, the detector is connected to the control module, thedetector is configured to transmit to the control module the objectivetype identifier of the projection objective connected to the opticaltransmission system, and the control module is further configured tocontrol the laser source and/or the optical transmission system, e.g.the deflection module and/or the optical correction element, based onthe objective type identifier. For example, the objective typeidentifier is implemented as a mechanical, optical, electrical or radiobased identifier. Through assignment and recognition of an objectivetype, the laser beam can be controlled in its condition, transmission,direction and/or deflection, depending on the optical characteristics ofthe used projection objective.

BRIEF DESCRIPTION OF THE DRAWINGS

A design of the present invention is described below with the aid of anexample. The example of the design is illustrated by the followingattached figures:

FIG. a shows a block diagram which illustrates schematically anophthalmological device being used to treat an eye by means of a focusedpulsed laser beam.

FIG. 1 b shows a plan view of a treatment surface, machined by theophthalmological device, and an image area lying thereupon.

FIGS. 2 a, 2 b, 2 c and 2 d respectively show a block diagram whichdiagrammatically illustrates an embodiment of the ophthalmologicaldevice being used to treat an eye by means of a focused pulsed laserbeam.

FIG. 3 a shows two pulsed laser beams of which the laser beam runningfurther removed from the optical axis is not imaged in a focused fashiononto a treatment surface.

FIG. 3 b shows two pulsed laser beams which are both imaged in a focusedfashion onto a treatment surface by means of a “corrected” lightprojection module.

FIG. 4 shows a block diagram which illustrates schematically anembodiment of the ophthalmological device having an objective changingdevice.

FIG. 5 shows a block diagram which illustrates schematically a frontview of an embodiment of the ophthalmological device having a number ofprojection objectives connected mechanically with each other.

FIG. 6 shows a block diagram which illustrates schematically a top viewof an embodiment of the ophthalmological device having a number ofprojection objectives connected mechanically with each other.

FIG. 7 a shows a block diagram which illustrates schematically anembodiment of the ophthalmological device having a number of applicationelements connected in each case to one of the projection objectives.

FIG. 7 b shows a block diagram which illustrates schematically anembodiment of the ophthalmological device having a common applicationelement for a number of projection objectives.

FIG. 7 c shows a block diagram which illustrates schematically acombined embodiment of the ophthalmological device having a number ofapplication elements connected to the projection objectives and having afurther common application element.

DETAILED DESCRIPTION OF THE EMBODIMENTS

In FIGS. 1 a, 2 a, 2 b, 2 c, 2 d, 4, 5, 6, 7 a, 7 b and 7 c thereference symbol 1 denotes an ophthalmological device or anophthalmological device arrangement with a laser source 17 and anoptical light projection module 11, optically connected to the lasersource 17, for generating and projecting in a focused fashion a pulsedlaser beam L′ for the punctiform breakdown of tissue at a focus F (focalpoint) in the interior of the eye tissue 21, for example in the cornea.The laser source 17 comprises, in particular, a femtosecond laser forgenerating femtosecond laser pulses which have pulse widths of typically10 fs to 1000 fs (1 fs=10−15 s). The laser source 17 is arranged in aseparate housing or in a housing common to the light projection module11. For the purpose of holding and applying the ophthalmological device1 or the optical light projection module 11 manually, theophthalmological device 1 has a diagrammatically illustrated handle 18.As is also illustrated diagrammatically in Figure la, theophthalmological device 1 comprises a holding element 19 forinterchangeably holding various optical light projection modules 11 orat least various objective element(s) of the light projection module 11.The holding element 19 is designed, for example, as a bayonet catch orscrew plug.

For the purpose of better understanding, it is to be stated here thatFIGS. 1 a, 2 a, 2 b, 2 c, 2 d, 4, 5, 6, 7 a, 7 b and 7 c illustrate theophthalmological device 1 diagrammatically and in a simplified fashion.For example, the figures do not reproduce precisely that the opticallight projection module 11 has a high numerical aperture of, forexample, at least 0.3, that the ophthalmological device 1 is fastened onthe eye 2 by means of a suction ring, and that the ophthalmologicaldevice 1 comprises a contact element (for example an applanationelement) for the contact based deformation (for example for applanation)of the eye 2 when the ophthalmological device 1 is being applied.

As is illustrated diagrammatically in Figure la, the ophthalmologicaldevice 1 comprises a deflection module 16, that is to say an opticalscanning module or scanner module which is set up to deflect thefemtosecond laser pulses L1 generated by the laser source 17 in at leastone direction, and thereby to move the focus F of the pulsed laser beamL′ in accordance with a scanning pattern (scan pattern) at least in onedirection x, y of the (continuous or discontinuous) defined treatmentsurface w in the tissue 21 of the eye 3. With the motionless lightprojection module 11 (static), a deflection of the femtosecond laserpulses L effects a movement of the focus F of the pulsed laser beam L′in the image area p which is situated on the treatment surface w andextends from the optical axis z of the light projection module 11 (seeFIG. 1 b). The image region p is thus scanned image point by image pointin accordance with the scanning pattern, individual image points alsobeing able to overlap one another partially or completely. In theapplied state of the ophthalmological device 1 or the light projectionmodule 11, the image area p runs substantially normal to the opticalaxis z, at least at the point of intersection with the optical axis z.It may be maintained here that the treatment surface w and the imagearea p can be more simply flat, but also curved. The image area p hasdifferent possible shapes, depending on the control of the deflectionmodule 16. For example, together with the laser source 17 the deflectionmodule 16 is arranged in a separate housing or in a housing common tothe light projection module 11.

In addition, in one variant the ophthalmological device 1 comprises adrive module 15 for moving the light projection module 11 along thedirections x and/or y and/or a normal to these directions (for examplealong the optical axis z). Thus, the drive module 15 can likewise movethe focus F of the pulsed laser beam L′ in one or more directions. Thefocus F of the pulsed laser beam L′ can also form the normal (z) bymeans of moveable lenses, for example inside the light projection module11.

As is illustrated in FIG. 1 a, the ophthalmological device 1additionally comprises a controllable optical correction element 14which is arranged in the diagrammatically illustrated beam path Lbetween the laser source 17 and the exit of the light projection module11. The optical correction element 14 is set up for the variablemodulation of the wavefront of the femtosecond laser pulses. The phasetransient times and/or the propagation directions are varied over thebeam cross section of the femtosecond laser pulses by the controllablemodulation of the wavefront. Furthermore, the polarization and theamplitude distribution can be varied. Since, given an unchanged spectraldistribution, the wavefront can be dependent in general on the amplitudedistribution, the polarization distribution and the phase distributionin the beam cross section, or can be influenced by these, it is intendedbelow to talk of a wavefront modulation in place of amplitude,polarization and phase modulation. The term wavefront modulation furthercomprises the modulation of the propagation directions. The opticalcorrection element 14 is designed, for example, as a deformable mirror,as a spatial transient time delay element, by means of moveable lenses,by means of moveable prisms, and/or as a diffractive optical element.Radially moveable lenses can be integrated, for example, in polarcoordinate scanner systems which deflect at a high annular, butcomparatively low radial speed. The optical correction element 14 canalso be designed by means of an anamorphotic optical module, a chromaticcrystal, a lens array, a spatial polarization plate, a diaphragm and/ora spatial light modulator (for example a conventional mirror array orLCD array).

The reference symbol 13 in FIGS. 1 a, 2 a, 2 b, 2 c, 2 d and 4 denotes acontrol module which is designed by means of software and/or hardware asa programmed logic module. The control module 13 is connected to theoptical correction element 14 for the purpose of transmitting controlsignals. The control module 13 is arranged in a separate housing or in ahousing common to the light projection module 11. The control module 13is set up to control the optical correction element 14 such that thewavefront of the femtosecond laser pulses is modulated so that thedeflected femtosecond laser pulses of the pulsed laser beam L′ arerespectively focused at the image point, this being, specifically, onthe treatment surface w for image points inside the entire image area p.

The image of two pulsed laser beams L3, L4 by the “uncorrected” lightprojection module 11 is illustrated in FIG. 3 a. As indicated by thefocus F3, the laser beam L3 running in the vicinity of the optical axisz is imaged in a fashion focused onto the treatment surface w. Bycontrast, the laser beam L4 deflected further from the optical axis z isimaged onto an (unsharp) focal area F4′ lying outside the treatmentsurface w. FIG. 3 b illustrates the imaging of the pulsed laser beamsL3, L4 by the “corrected” projection system 11-14, which comprises thelight projection module 11 and the optical correction element 14, thecorrection element 14 being controlled by the control module 13 suchthat the wavefront of the femtosecond laser pulses is modulated suchthat both the laser beam L3, at the focus F3, and the laser beam L4, atthe focus F4, are imaged in a focused fashion onto the image area p ofthe treatment surface w. The control of the optical correction element14 is performed dependent on the deflection of the femtosecond laserpulses L1, generated by the laser source 17, by the deflection module16. The deflection of the femtosecond laser pulses L1 is defined, forexample, by x/y coordinates in the image area p, or by one or moredeflection angles. Data on the deflection are, for example, transmittedby the deflection module 16 to the control module 13, or are alreadyknown to the control module 13 from internal control data. In addition,the control of the optical correction element 14 is performed as afunction of stored control data 131 and/or feedback relating to theprojection of the pulsed laser beam L′ in the image area p on thetreatment surface w. For the different deflections (deflection values),the control data comprise control values for controlling the opticalcorrection element 14. The control data are permanently defined, forexample on the basis of the calculation of the optical system, or of acalibration of the optical system after its assembly, by means ofexternal measuring instruments, or are generated by means of an optionalcalibration module 132 on the basis of feedback relating to theprojection of a laser beam into the image area p on the treatmentsurface w.

Feedback via the projection into the image area p on the treatmentsurface w is performed by means of optical elements and of the optionaldetector module 12. In particular for the purpose of calibration beforeoperational use, the femtosecond laser pulses of the projected laserbeam L′, or an auxiliary reference laser beam from the optionalreference laser source 171, are detected by removable or moveableoptical elements, for example mirrors, semitransparent mirrors and/orlenses, at the level of the treatment surface w, and then optically tothe detector module 12. For feedback during operational use, thefemtosecond laser pulses which are reflected onto the treatment surfacew are fed to the detector module 12 via optical elements, for example bymeans of reflecting and/or semitransparent mirrors and/or lenses. In analternative embodiment, the device 1 comprises optical elements, forexample mirrors, semitransparent mirrors and/or lenses, which simulate areference beam path corresponding to the beam path used for projectingthe femtosecond laser pulses onto the treatment surface w such that thedetector module 12 can be fed femtosecond laser pulses whose wavefrontand/or beam profile correspond to those of femtosecond laser pulses ofthe laser beam L′ in the image area p on the treatment surface w. Itwill be understood by the person skilled in the art that, as in the caseof calibration, feedback during operational use is generated inalternative embodiments on the basis of an additional auxiliaryreference laser beam which is generated by the optional reference lasersource 171.

In a number of embodiments, the detector module 12 comprises a wavefrontdetector and/or a light beam profile detector for determining thewavefront profile or the light beam profile of the femtosecond laserpulses fed via the optical elements. The wave-front detector is, forexample, designed as a Shack-Hartmann sensor, for example according toUS 2003/0038921, or as an interferometer, for example as a shearinginterferometer. Further possible embodiments of the wavefront detectorare described in Jos. J. Rozema, Dirk E. M. Van Dyck, Marie-JoseTassignon, “Clinical comparison of 6 aberrometers. Part 1: Technicalspecifications”, J Cataract Refract Surg, Volume 31, June 2005, pages1114-1127. The light beam profile detector comprises, for example, a CCD(Charge Coupled Device) chip. The detector module 12 is connected to thecontrol module 13 for feeding back the specific wavefront profile or thelight beam profile. The control module 13 is set up to generate controlsignals on the basis of the feedback, and to lead them to the opticalcorrection module 14 in order to modulate the wavefront of thefemtosecond laser pulses by means of the optical correction module 14such that a desired, defined wavefront profile or a desired, definedlight beam profile results in the image area p on the treatment surfacew, and the deflected femtosecond laser pulses are adequately focused onthe treatment surface w over the entire image area p in accordance witha defined degree of focus. Depending on the machining method, there canbe a number of quality criteria for the degree of focus. For example,the maximum intensity at the focus can be defined as degree of focus(important for initiating an optical breakthrough). Furthermore, theshape of the focus (for example circular for a defined machining zone,elliptical as a function of scanning patterns), the diameter thereof(important in the case of uniform spot spacing) or else the intensityprofile (for example flat top) can serve as a criterion for the degreeof focus. If the focus shape (spot shape) is the decisive criterion,this can be readjusted in the event of an unsatisfactory intensity atthe laser source. The readjustment can also be undertaken as a functionof the focal position. The readjustment can be required, for example,when the wavefront modulator gives rise to fluctuating intensities.

In the embodiment according to FIG. 2 a, the controllable opticalcorrection element 14 is inserted into the beam path between the lasersource 17 and the deflection module 16. The femtosecond laser pulses L1generated by the laser source 17 are fed to the correction element 14,which modulates the wavefront of the femtosecond laser pulses L1 inaccordance with the control signals of the control module 13, doing soin each case for the image point onto which they are deflected andprojected in the image area p. The femtosecond laser pulses L2 generatedby the correction element 14 and having a modulated wavefront are fed tothe deflection module 16. The deflection module 16 deflects thefemtosecond laser pulses L2 in at least one scanning direction. Thefemtosecond laser pulses L2′ deflected by the deflection module 16 arefed to the light projection module 11 for the purpose of focusedprojection.

In the embodiment according to FIG. 2 b, the controllable opticalcorrection element 14 is integrated in the deflection module 16. Thefemtosecond laser pulses L1 generated by the laser source 17 are fed tothe deflection module 16. In the internal beam path of the deflectionmodule 16, the correction element 14 modulates the wavefront of thefemtosecond laser pulses L1 in accordance with the control signals ofthe control module 13, doing so in each case for the image point ontowhich they are deflected and projected in the image area p. Thefemtosecond laser pulses L2″ with modulated wavefront, which aremodulated by the correction element 14 and deflected by the deflectionmodule 16 in at least one scanning direction, are fed to the lightprojection module 11 for focused projection.

In the embodiment according to FIG. 2 c, the controllable opticalcorrection element 14 is inserted into the beam path between thedeflection module 16 and the light projection module 11. The femtosecondlaser pulses L1′, generated by the laser source 17 and deflected by thedeflection module 16, are fed to the correction element 14. Thecorrection element 14 modulates the wavefront of the deflectedfemtosecond laser pulses L1′ in accordance with the control signals ofthe control module 13, doing so in each case for the image point ontowhich they are deflected and projected in the image area p. Thefemtosecond laser pulses L2′″ with modulated wavefront, which aredeflected by the deflection module 16 in at least one scanning directionand are modulated by the correction element 14, are fed to the lightprojection module 11 for focused projection. In the case of a deflectingmirror in the deflection module 16, said mirror can also simultaneouslybe designed with a capacity to be deformed or to modulate intensity, andcan thus also serve as optical correction element. Furthermore, inaddition to correction based on wavefront modulation it is alsopossible, for example, to use a deformable mirror for adjusting(positioning) the focus.

In the embodiment according to FIG. 2 d, the controllable opticalcorrection element 14 is integrated in the light projection module 11.The femtosecond laser pulses L1 generated by the laser source 17 are fedto the deflection module 16, which deflects the femtosecond laser pulsesL1 in at least one scanning direction. The deflected femtosecond laserpulses L1′ are fed to the correction element 14 in the light projectionmodule 11, which modulates the wavefront of the deflected femtosecondlaser pulses L1′, doing so in each case for the image point onto whichthey are deflected and projected in the image area p. The femtosecondlaser pulses with modulated wavefront, which are generated by thecorrection element 14, are projected in a focused fashion by the lightprojection module 11.

FIG. 4 shows an embodiment of the ophthalmological device 1 with theholding element 19 being implemented as an objective changing device 4.In FIGS. 4, 5, 6, 7 a, 7 b, 7 c reference numeral 5 refers to theoptical transmission system for transmitting the femtosecond laserpulses from the laser source 17 to a projection objective 3 of theprojection module 11. Preferably, the optical transmission system 5 isconfigured to convey essentially in parallel the laser beams L to theprojection objective 3, which is not the case for interchangeableobjectives used in photography, for example. Depending on theembodiment, the optical transmission system 5 comprises the deflectionmodule 16, the optical correction module 14 and/or the detector module12 described above.

The objective changing device 4 is configured for changing theprojection objective 3 and to connect the currently selected projectionobjective 3 to the optical transmission system 5. Different embodimentsof the objective changing device 4 are illustrated in FIGS. 4, 5, 6, 7a, 7 b and 7 c.

In the embodiment according to FIG. 4, the objective changing device 4comprises a connecting module 41 for removably inserting, receiving andconnecting the projection objective 3 to the optical transmission system5. For example, the connecting module 41 comprises a thread or bayonetconnector for receiving and fixing the projection objective 3 to theophthalmological device 1. When it is in the fixed state, the projectionobjective 3 is connected optically with the optical transmission system5.

In the embodiments according to FIGS. 5, 6, 7 a, 7 b and 7 c, theobjective changing device 4 a, 4 b comprises in each case a number ofdifferent projection objectives 3, 3′ which are connected mechanicallywith each other (e.g. two, three or more projection objectives). Theprojection objectives 3, 3′ are provided in each case with an objectivetype identification, and differ in their optical characteristics, suchas numerical aperture, focal length, field size, field curvature, focusdiameter, focus shape, focus extension in projection direction and/orbeam divergence.

In the embodiment according to FIG. 5, the objective changing device 4 ais configured to change the projection objectives 3, 3′ by way of rotarymotion φ about a rotation axis r. The projection objectives 3, 3′ arefixed to a carrier (support) which is rotatable about the rotation axisr. For example, the objective changing device 4 a is implemented in formof revolver optics. By way of a rotary motion φ, a selected one of theprojection objectives 3, 3′ is conveyed (supplied) and connectedoptically to the optical transmission system 5.

In the embodiment according to FIG. 6, the objective changing device 4 ais configured to change the projection objectives 3, 3′ by way oftranslatory motion t. The projection objectives 3, 3′ are fixed to acarrier slide which is movable along an axis. By way of a translatorymotion t, a selected one of the projection objectives 3, 3′ is conveyed(supplied) and connected optically to the optical transmission system 5.

Preferably, when it is connected to the optical transmission system 5,the selected projection objective 3, 3′ is fixed in its rotation ortranslation, respectively, for example, mechanically by means of alocking or blocking mechanism.

In an embodiment, the carrier of the objective changing device 4 a, 4 bhas one or more connecting modules for removably receiving in each caseone projection objective 3, 3′, as described in the context of FIG. 4.Thereby, the objective carrier can be loaded with different sets ofprojection objectives 3, 3′, provided, for example, for differenttreatment steps and applications performed during treatment of apatient.

As illustrated schematically in FIG. 4, the ophthalmological device 1comprises an objective detector 6 for detecting the objective typeidentifier of the connected projection objective 3. For example, theobjective type identifier is implemented as a mechanical, optical,electrical or radio based identifier, and indicates a type code assignedto the objective type identifier. Corresponding to the embodiment of theobjective type identifier, the objective detector 6 comprises a sensorfor detecting and reading a mechanically implemented identifier, e.g. acode implemented by way of structural elements, for capturing anoptically implemented identifier, e.g. a bar code or a blind coding, forreading an electrically implemented identifier, e.g. a capacitive orohmic code, or for receiving and recognizing a radio based identifier,e.g. an RFID (Radio Frequency Identification).

The objective detector 6 is connected to the control module 13 and isconfigured to transmit the determined objective type identifier to thecontrol module 13. For transmitting control signals (control commands,control programs), the control module 13 is connected to the deflectionmodule 16, the controllable optical correction element 14, and the lasersource 8. The control module 13 is arranged in a separate housing or ina housing shared with the objective changing device 4. For differentobjective types, the control module 13 comprises in each case assignedphysical nominal values, which indicate optical characteristics of therespective objective type, e.g. numerical aperture, focal length, fieldsize, field curvature, focus diameter, focus shape, focus extension inprojection direction and/or beam divergence, and/or assigned controlprogram modules. The control module 13 is configured to control thelaser source 8 and the optical transmission system 5, particularly thedeflection module 16 and the correction element 14, based on thedetected objective type identifier, by transmitting to the laser source8, the correction element 14, the deflection module 16 and/or othercontrollable elements of the optical transmission system 5, e.g. movablelenses and controllable blinds, control commands from assigned controlprogram modules and/or in dependence of assigned physical nominalvalues. Thus, depending on the objective type used, adapted and changedautomatically is the laser beam L of the laser source 8, e.g. its energylevel, pulse rate, and/or pulse width, as well as its transmission,direction and/or deflection.

In FIG. 4, the reference numeral 9 refers to a measuring system fordetermining the position of the projection objective, connected to theoptical transmission system 5, relative to the ophthalmological device1, and particularly relative to the optical transmission system 5. Indifferent embodiments, the measuring system 9 is configured to determinethe relative position in a capacitive, inductive, ohmic or opticalfashion. The measuring system 9 is connected to the control module 13and configured to transmit to the control module 13 the determinedrelative position. Depending on the embodiment, the control module 13indicates to the user via a user interface, e.g. acoustically and/oroptically, deviations of the relative position from a defined range oftolerance, and/or adapts according to the deviation from a definedtarget value the controlling of the laser source 8 and/or the opticaltransmission system 5, particularly the deflection module 16.

Although this is not illustrated explicitly in the simplified FIGS. 4,5, 6, 7 a, 7 b and 7 c, in respective embodiments, the ophthalmologicaldevice 1 shown in these Figures also comprises a control module 13, anobjective detector 6, and/or a measuring system 9 for determining typeand position, as well as for controlling the laser beam L based thereon.

FIGS. 7 a, 7 b, 7 c show embodiments in which the ophthalmologicaldevice 1 has one or more application elements 30, 31, 31. For example,the application elements 30, 31, 31 comprise contact bodies, e.g.applanation bodies which are at least in places or partiallytransparent, or concave/convex form bodies. Depending on the embodiment,the application elements 30, 31, 31 further comprise a suction ring orother fastening devices for fixing on the eye 2.

In the embodiment according to FIG. 7 a, the application elements 30,31, 31 are in each case attached to the projection objectives 3, 3′ in afixed or interchangeable manner, and can be implemented differently, forexample, e.g. as an applanation body, a concave form body or differentdistance bodies for different treatment steps, and/or with, without orwith different fixing means for fixing on the eye 2.

In the embodiment according to FIG. 7 b, the ophthalmological device 1has a common fixed or interchangeable application element 30, and theobjective changing device 4 is configured and arranged such that thedifferent projection objectives 3, 3′ can be interchanged such that theycan be combined with the application element 30, without contact or withmechanical contact, when the projection objectives 3, 3′ are connectedto the optical transmission system 5.

The embodiment according to FIG. 7 c is a combination of the embodimentsaccording to FIGS. 7 a and 7 b, whereby, on one hand, differentapplication elements 31, 31′ are attached to the projection objectives3, 3′ in each case, and, on the other hand, the ophthalmological device1 has a common application element 30. In the combined embodimentaccording to FIG. 7 c, it is possible during an operation to select andinterchange different projection objectives 3, 3′ and/or applicationelements 31, 31′, on one hand, and, on the other hand, a commonapplication element 30 can be kept during the treatment, for example asuction ring for fixing on the eye 2, a distance body and/or aprotection blind.

Although this is not illustrated, the application elements 30, 31, 31′can also be combined with the embodiments according to FIGS. 4 and 6.

In a further embodiment, the objective changing device 4, 4 a, 4 bfurther comprises an optional drive module for interchanging in amotorized manner the projection objectives 3, 3′ and/or the applicationelements 31, 31′.

What is claimed is:
 1. An ophthalmological device, comprising: anoptical light projection module for projecting femtosecond laser pulsesonto a defined treatment surface, a controllable optical correctionelement configured to variably modulate the wavefront of the femtosecondlaser pulses, and a control module connected to the optical correctionelement and configured to control the optical correction element in sucha way that the femtosecond laser pulses are focused on the definedtreatment surface in accordance with a defined degree of focus.
 2. Theophthalmological device of claim 1, wherein the control module isconfigured to control the optical correction element in such a way thatthe femtosecond laser pulses are focused on the defined treatmentsurface in accordance with a degree of focus defined by a qualitycriteria, the quality criteria including at least one of: intensity ofthe focus, intensity profile of the focus, shape of the focus, anddiameter of the focus.
 3. The ophthalmological device of claim 1,wherein the control module is configured to control the opticalcorrection element in such a way that the femtosecond laser pulses arefocused on the treatment surface in an image area, extending from theoptical axis of the light projection module, in accordance with thedefined degree of focus.
 4. The ophthalmological device of claim 1,further comprising a scanner module configured to deflect thefemtosecond laser pulses in at least one direction, wherein the opticalcorrection element is arranged upstream from the scanner module.
 5. Theophthalmological device of claim 1, further comprising a scanner modulecon-figured to deflect the femtosecond laser pulses in at least onedirection, wherein the control module is configured to control theoptical correction element as a function of a deflection of thefemtosecond laser pulses in such a way that the femtosecond laser pulsesare focused on the treatment surface in an image area, extending fromthe optical axis of the light projection module.
 6. The ophthalmologicaldevice of one of claim 3 or 5, wherein the optical light projectionmodule has a numerical aperture of at least 0.3, and the image area onthe treatment surface has a diameter of at least 10 mm.
 7. Theophthalmological device of claim 1, further comprising optical elementsfor detecting the femtosecond laser pulses projected onto the treatmentsurface, wherein the control module is configured to control the opticalcorrection element as a function of detected femtosecond laser pulsesprojected onto the treatment surface.
 8. The ophthalmological device ofclaim 1, wherein the control module is configured to control the opticalcorrection element as a function of feedback relating to the projectionof the femtosecond laser pulses onto the treatment surface to modulatethe wavefront of the femtosecond laser pulses such that the femtosecondlaser pulses are projected onto the treatment surface in accordance withthe defined degree of focus.
 9. The ophthalmological device of claim 1,further comprising a detector module including at least one of: awavefront detector and a light beam profile detector for determining awavefront profile or light beam profile of the laser pulses, wherein thecontrol module is configured to control the optical correction elementas a function of the wavefront profile or light beam profile,respectively.
 10. The ophthalmological device of claim 1, wherein theoptical correction element is configured to modulate the wavefront ofthe femtosecond laser pulses by varying at least one of the parameterscomprising phase distribution, amplitude distribution, polarizationdistribution and propagation directions in the beam cross section of thefemtosecond laser pulses.
 11. The ophthalmological device of claim 1,wherein the optical correction element comprises at least one ofdeformable mirror, spatial transient time delay element, moveablelenses, moveable prisms, diffractive optical element, anamorphoticoptical module, photonic crystal, lens array, spatial polarizationplate, diaphragm and spatial light modulator.
 12. The ophthalmologicaldevice of claim 1, wherein the optical correction element and thecontrol module are set up to dynamically modulate the wavefront of thefemtosecond laser pulses.
 13. The ophthalmological device of claim 1,wherein the optical correction element and the control module are set upto modulate the wavefront of the femtosecond laser pulses sequentiallyin each case for an image point lying on the treatment surface.
 14. Theophthalmological device of claim 1, further comprising optical elementsfor simulating a reference beam path corresponding to a beam path usedfor projecting the femtosecond laser pulses onto the treatment surface,and for detecting femtosecond laser pulses projected in the referencebeam path, wherein the control module is configured to control theoptical correction element as a function of detected femtosecond laserpulses projected in the simulated beam path.
 15. The ophthalmologicaldevice of claim 1, further comprising a laser source configured togenerate a reference laser beam, wherein the control module isconfigured to control the optical correction element as a function ofthe reference laser beam deflected and projected in accordance with thefemtosecond laser pulses.
 16. An ophthalmological device, comprising: anoptical light projection module for projecting femtosecond laser pulsesinto eye tissue, a controllable optical correction element configured todynamically modulate the wavefront of the femtosecond laser pulses, anda control module connected to the optical correction element andconfigured to control the optical correction element in such a way thatthe optical correction element dynamically modulates the wavefront ofthe femtosecond laser pulses for adjusting and positioning the focus ofthe femtosecond laser pulses in direction of the optical axis of theoptical light projection module.